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<h1>Tiny PIC bootloader</h1>
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<h2>Tiny Bootloader</h2>

<p>I consider firmware programs should be as small and as fast as possible. In the bootloader case all the hard work can be 
moved to PC software, allowing a wider range of options and easier upgrades to the software, 
while the firmware can implement only the basic functions.</p>

<div align=center>
<b>Download</b> <a href="tinybld173.zip"><b>tinybld173</b></a>&nbsp; Apr,2005</div>
<div align=center>&nbsp;</div>
<div align=center>some older versions:</div>
<div align=center>
	<table border="1" width="200" style="border-collapse: collapse" id="table1">
		<tr>
			<td> 


<a href="tinybld17.zip"><font size="2">tinybld17</font></a></td>
			<td><font size="2">Nov,2004</font></td>
		</tr>
		<tr>
			<td>
<a href="tinybld14.zip"><font size="2">tinybld14</font></a></td>
			<td><font size="2">June,2003</font></td>
		</tr>
	</table>
</div>
<hr color="#000000" width="50%">


<p>

</p>
<h4>Features of the firmware</h4>
<ul>
<li>Size of only 100 words; (both versions, for 16F and for 18F occupy less than 100 words);
<li>Can write flash, eeprom and configuration bytes(18F);
<li>On reset, waits 1 second for a message from the PC, if not received, launch user application;
<li>Developed initially for: 16F876A, 16F877A, 18F252; <i>should work (with modifications)</i> on most 16F and 18F PICs;</li>
<li>Reported to work with 16F873, 16F873A, 16F876, 16F877, 18F452, 18F2620, 18F8720, 18F8680, 18F4320, 18F1x20, 
16F88; 18F2620;</li>
<li>The .asm file can be easily modified and adapted for any frequency (or baudrate);</li>
</ul>
<h4>Features of the PC software</h4>
<ul>
<li>Can upload  programs into flash  (in current version eeprom and cfg bytes can be modified only from command line);
<li>Works with both PIC 16F and 18F types; automatically detects PIC type, model, HEXcontent;
<li>Remembers last settings;
<li>In case of errors, performs retransmissions or tries to resynchronize with pic;
<li>The communication settings are editable so you can write any COM number or 
desired baud;<li>If a filename is specified as a command line parameter, it will 
automatically try to write it;<li>Several features can be activated from 
&quot;Options&quot;, others by writing the command in the log window. Start typing &quot;help&quot; or &quot;?&quot; on an empty line:<br>&nbsp;
<table border="1" cellspacing="1" style="border-collapse: collapse" bordercolor="#111111" width="100%" id="AutoNumber1">
	<tr>
		<td width="30%"><font face="Courier" size="2">?</font></td>
		<td width="70%"><font face="Courier" size="2">help</font></td>
	</tr>
	<tr>
		<td width="30%"><font face="Courier" size="2">ontop </font></td>
		<td width="70%"><font size="2">keep the window on top of the others</font></td>
	</tr>
	<tr>
		<td width="30%"><font face="Courier" size="2">logdetails </font></td>
		<td width="70%"><font size="2">lists detailed stuff happening inside (used only for debugging)</font></td>
	</tr>
	<tr>
		<td width="30%"><font face="Courier" size="2">clearallflash </font></td>
		<td width="70%"><font size="2">clears all flash except the bootloader (actually it <b>fills</b> 
    all flash with FFh)</font></td>
	</tr>
	<tr>
		<td width="30%"><font face="Courier" size="2">writeeeprom &lt;addr&gt; &lt;dat&gt;</font></td>
		<td width="70%"><font size="2">writes the byte &lt;dat&gt; at the address &lt;addr&gt; (numbers can be 
    either dec or hex)<br>eg: <font face="Courier">&nbsp; writeeeprom 0 b6h&nbsp;&nbsp;&nbsp; 
		</font>&nbsp;- 
    writes B6h in the first eeprom location</font></td>
	</tr>
	<tr>
		<td width="30%"><font face="Courier" size="2">writeconfig &lt;adrLow&gt; &lt;dat&gt;</font></td>
		<td width="70%"><font size="2">only for 18F; writes the configuration byte &lt;dat&gt; at the 
    address 300000h+&lt;addrLow&gt;<br>eg: <font face="Courier">&nbsp; writeconfig 3 FFh&nbsp;&nbsp;&nbsp; 
		</font>&nbsp;- 
    activates WDT</font></td>
	</tr>
	</table>
</ul>

<p align="center">&nbsp;<img border="0" SRC="tinyBldWin.gif" width="346" height="125"></p>
<h4>What do you need</h4>
<ul>
<li>MPASM installed</li>
<li>Know how to use MPASM IDE (or Mpasmwin.exe) to modify and assemble an asm 
file.</li>
<li>You must have the PIC (pins TX,RX) connected to the serial port of the PC 
(pins Rx,Tx), usually using a MAX232 level converter:<br>
<img border="0" src="max232.gif" width="450" height="236">
</ul>
<p></p>
<h4>How to use</h4>
<ul>
<li>The program must meet this requirement: it must have in the first 4words of 
memory a GOTO to the start of the main program. (this is what the majority of the bootloaders require). 
So in assembler it should look something like this:<table width=300 style="border-collapse: collapse; font-family:courier; font-size: 75%; padding: 0 3 0 3;" border="1">
<tr>
<th>PIC16F</th>  
<th>PIC16F</th>  <th>PIC18F</th>
</tr>
<tr>
<td>org 0<br>;clrf STATUS<br>clrf PCLATH<br>goto Main</td>  
<td>org 0<br>;clrf STATUS<br>pagesel Main<br>goto Main</td>  
<td>org 0<br>goto Main<br>
<br>
&nbsp;</td>
</tr>
</table>
<li>If you use a compiler, search the help for a directive that allows 
coexistence with a bootloader;<li>Modify &quot;xtal&quot;, &quot;baud&quot;, &quot;_??_OSC&quot; to what you need; assemble it 
(for example with .\MPLAB\MCHIP_Tools\Mpasmwin.exe); write the 
HEX it with a PIC programmer; put the PIC on you board and connect it to the PC 
serial port.<li>You can keep the TinyBootloader interface opened, browse or enter the name 
of the hex file, select the COM port and baud rate, then click WriteFlash, or 
double-click the tray icon, and after that reset (or power-up) the PIC.<li>If all things are set up properly the program will be loaded into the pic and 
executed.</ul>
<ul type="circle">
<li>When you press &quot;WriteFlash&quot; the application will read and analyze the hex 
file to determine if it's a 16F or 18F code, and to determine the size, eeprom and 
config data.</li>
<li>Then it will ping the serial port until there is a response from the PIC or 
until the timeout will expire.</li>
<li>On the other side, the PIC (after reset), it will wait around 1s to receive something 
from the PC. This timeout value can be adjusted from &quot;movlw xtal/2000000+1&quot;, but 
decreasing this timeout too much will cause later communication to fail.</li>
<li>A warning will be issued if: a goto is not found in the first 4 instructions 
or if PIC and HEX files do not match.</li>
</ul>

<p>All critics and suggestions are welcome at:&nbsp; <img src="../clmail.gif" width="169" height="15"></p>




<h2>General info about Bootloaders</h2>




<p>A bootloader is a program that stays in the microcontroller and communicates 
with the PC (usually through the serial interface). The bootlader receives a 
user program from the PC and writes it in the flash memory, then launches this 
program in execution. Bootloaders can only be used with those microcontrollers 
that can write their eeprom through software. The bootloader itself must be 
written into the flash memory with an external burner. In order for the 
bootloader to be launched after each reset, a &quot;goto bootloader&quot; instruction must 
exist somewhere in the first 4 instructions; it is the job of the bootloader to 
reallocate the first 4 instructions of the user program to another location and 
execute them when the bootloader exits.<br>
<img border="0" src="bootloader.gif" width="327" height="388"></p>




<p>(Some of the) Available bootloaders (as reported by Google) in May, 2003:</p>

<TABLE border=1 cellpadding="1" cellspacing="1" width="634"
		style="border-collapse: collapse; font-size: 75%; padding: 0 3 0 3;">
<TR>
	<TH>Bootloader Name / Author</TH>
	<TH>Supported models</TH>
	<TH>Size(words)</TH>
	<TH>Comments</TH>
</TR>
<TR>
	<TD><A HREF="http://www.microchip.com/">From Microchip</A><br>&nbsp;</TD>
	<TD>16F,18F</TD>
	<TD align=right>1000</TD>
	<TD>uses Hyperterminal to upload hex files</TD>
</TR>
<TR>
	<TD><A HREF="http://www.microchipc.com/">From MicrochipC</A><BR>&nbsp;</TD>
	<TD>16F,16F*A,18F</TD>
	<TD align=right>256/2000</TD>
	<TD>+ok</TD>
</TR>
<TR>
	<TD><A HREF="http://www.voti.nl/wloader/index_1.html">WLoader</A><br>Wouter van Ooijen</TD>
	<TD>16f877</TD>
	<TD align=right>1000</TD>
	<TD>+does not use the UART, <br>
    +the serial interface use only one I/O pin </TD>
</TR>
<TR>
	<TD><a href="http://www.circuitcellar.com/flash2002/honorable.htm">ZPL</a><BR>Wouter van Ooijen</TD>
	<TD>18F</TD>
	<TD>
    <p align="right">384</TD>
	<TD>+unusual method using mclr: uses zero I/O pins !</TD>
</TR>
<TR>
	<TD><A HREF="http://www.seanet.com/~karllunt/picload.htm">KarlLunt</A><BR>&nbsp;</TD>
	<TD>16f87x</TD>
	<TD align=right>512</TD>
	<TD>-activation on input pin<br>
    -derived from Microchip boot877.asm (uses Hyperterminal)</TD>
</TR>
<TR>
	<TD><A HREF="http://www.dontronics.com/rfarmer.html">PICLOADER</A><BR>Rick Farmer </TD>
	<TD>PIC16F87x</TD>
	<TD align=right>2000</TD>
	<TD>-program must start at 0x3; +password<br>
    (uses Hyperterminal)</TD>
</TR>
<TR>
	<TD><A HREF="http://www.nyx.net/~jpurbric/picstuff.htm">bootload</A><BR>&nbsp;</TD>
	<TD>PIC16F877</TD>
	<TD align=right>800</TD>
	<TD>-written in C<br>
    -command line DOS program</TD>
</TR>
<TR>
	<TD><A HREF="http://www.thebytefactory.com/">theByteFactory</A><BR>&nbsp;</TD>
	<TD>16F877</TD>
	<TD align=right>1000</TD>
	<TD>-written in C<br>
    (uses Hyperterminal)</TD>
</TR>
<TR>
	<TD><A HREF="http://members.rogers.com/martin.dubuc/Bootloader/">Jolt</A><BR>
    Martin Dubuc</TD>
	<TD>18F</TD>
	<TD align=right>256</TD>
	<TD>-user code and interrupt vectors need to be relocated;<br>
&nbsp;Java GUI, +auto detect baud</TD>
</TR>
<TR>
	<TD><a href="http://www.htsoft.com">?</a><br>
    HI-TECH Software</TD>
	<TD>16F87x</TD>
	<TD align=right>256</TD>
	<TD>-written in C</TD>
</TR>
<TR>
	<TD><a href="http://www.ehl.cz/pic/pic_e.htm">PIC downloader</a><br>
    Petr Kolomaznik</TD>
	<TD>16F876</TD>
	<TD align=right>256</TD>
	<TD>-is rewritten and modified from HI-TECH<br>
    +Windows interface</TD>
</TR>
<TR>
	<TD><A HREF="http://www.johnsrud.no/pic/index.php">Ivar</A> Johnsrud<BR>&nbsp;</TD>
	<TD>18Fxx2/18Fxx8</TD>
	<TD align=right>360</TD>
	<TD>-bootloader based on HiTech's<br>
    -downloader based on Petr Kolomaznik's</TD>
</TR>
<TR>
	<TD><A HREF="http://home.hiwaay.net/~jeffj1/projects/bootloader/">B</A> 
    Bootloader<BR>&nbsp;</TD>
	<TD>PIC16F87x, PIC16F87xA</TD>
	<TD align=right>340</TD>
	<TD>-called only by user application <br>
    -written in C +Linux uploader</TD>
</TR>
<TR>
	<TD><A HREF="http://www.mcjournal.com/articles/arc103/arc103.htm">SGupta</A><BR>&nbsp;</TD>
	<TD>16f876</TD>
	<TD align=right>256</TD>
	<TD>&nbsp;</TD>
</TR>
<TR>
	<TD colSpan=4 align=center>I put mine here, for comparison:</TD>
</TR>
<TR>
	<TD>Tiny</TD>
	<TD>16F876A, 18F252, ...</TD>
	<TD align=right>100</TD>
	<TD>+details above</TD>
</TR>
</TABLE>

&nbsp;<p>I did it mainly because:<br>
1. Some bootloaders I used previously had some unpleasant bugs or didn't support 
the devices I had. <br>
2. I wanted to do it small. Actually it can be done even smaller :) but I like 
the size of 100;</p>
<p><br>
<br>


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